JP6671140B2 - Thermoplastic resin and method for producing the same - Google Patents

Description

  The present invention relates to a thermoplastic resin and a method for producing the same. More specifically, the present invention relates to a thermoplastic resin composition capable of greatly reducing foreign matter defects when forming a retardation film, and a method for producing the thermoplastic resin composition.

  The use of the liquid crystal display device is expanding year by year as a space-saving image display device with low power consumption. In recent years, with the progress of optical design technology, and in order to improve the appeal of consumers to liquid crystal display devices, a retardation film that can support various optical designs has been required. For example, an in-plane switching (IPS) mode, which is one of the liquid crystal display modes, is characterized in that a certain high viewing angle can be realized without using a retardation film. However, due to the optical characteristics of the liquid crystal cell, light leakage occurs when viewing the screen from an oblique direction, causing a reduction in the contrast of the displayed image due to so-called "floating black". And controlling light leakage.

  The refractive index in the thickness direction of the IPS mode liquid crystal cell is smaller than the refractive index in the in-plane direction. Therefore, a “negative retardation film” having a negative retardation Rth in the thickness direction is required for controlling light leakage. The retardation Rth was such that the refractive index of the slow axis in the film plane was nx, the refractive index of the fast axis in the film plane was ny, the refractive index in the thickness direction of the film was nz, and the thickness of the film was d. Sometimes given by the formula {(nx + ny) / 2-nz} × d. The negative retardation film can be obtained by stretching a resin having negative intrinsic birefringence.

  In addition, the members of the liquid crystal display device are required to have good balance of molding workability and surface hardness, and to have high light transmittance and low wavelength dependency, as well as high heat resistance. Polymethyl methacrylate, which is widely used as an optical material, has a negative intrinsic birefringence, but has a slightly lower glass transition temperature (Tg) of about 100 ° C., and improvement has been demanded. Therefore, an acrylic polymer having a ring structure in the main chain has been developed as an acrylic resin having both high light transmittance and high heat resistance (Patent Document 1). However, since the ring structure of the main chain has a positive intrinsic birefringence, it could not be applied to a negative retardation film. Therefore, an acrylic polymer having a ring structure in the main chain having a positive intrinsic birefringence and a copolymer containing a vinyl cyanide monomer unit and an aromatic vinyl monomer unit having a negative intrinsic birefringence. A negative retardation film obtained by stretching a thermoplastic resin composition containing the same has been developed (Reference 2).

JP 2007-262396 A JP 2010-262253 A

  However, a negative resin obtained by stretching a resin composition containing an acrylic polymer having a ring structure in the main chain and a copolymer containing a vinyl cyanide-based monomer unit and an aromatic vinyl-based monomer unit is obtained. The retardation film has a problem that there are many defects of foreign matters in the film. The present invention has been made in view of the above problems, and has as its object a negative position obtained by stretching a thermoplastic resin composition containing an acrylic polymer having a ring structure in its main chain and a styrene polymer. An object of the present invention is to provide a film having less foreign matter defects in a phase difference film.

  As a result of the study by the present inventors, the problem of the foreign matter defect of the film is that a low retardation film having a low content of a copolymer containing a vinyl cyanide-based monomer unit and an aromatic vinyl-based monomer unit, In a positive retardation film stretched only with an acrylic polymer having a ring structure in the main chain, which does not include a copolymer containing a vinylated monomer unit and an aromatic vinyl monomer unit, such a phenomenon occurs. In addition, foreign matter defects increase only when an acrylic polymer having a ring structure in the main chain and a copolymer containing a vinyl cyanide-based monomer unit and an aromatic vinyl-based monomer unit are present in a specific ratio. It turned out to be an issue. Further, various analyzes revealed that the foreign matter was derived from a copolymer containing an acrylic polymer having a ring structure in the main chain, a vinyl cyanide monomer unit and an aromatic vinyl monomer unit.

  That is, in the method for producing a thermoplastic resin composition according to the present invention which has solved the above problems, the content of the acrylic polymer having a ring structure in the main chain is not less than 51% by weight and not more than 75% by weight; A method for producing a thermoplastic resin wherein the content of a copolymer containing a monomer unit and an aromatic vinyl monomer unit is 25% by weight or more and 49% by weight or less, wherein the acrylic polymer is used as a catalyst. By performing a cyclization condensation reaction by using an acidic substance or a basic substance, a cyclization step of obtaining an acrylic polymer having a ring structure in the main chain, and a basic substance when an acidic substance is used as the catalyst, When a basic substance is used as the catalyst, the method includes a neutralization step of neutralizing with an acidic substance, and the amount of the basic substance or the acidic substance used in the neutralization step is the amount of the catalyst used in the cyclization step. It is characterized by the use 0.2 molar equivalents to 0.9 molar equivalents or less with respect to the dose.

In the thermoplastic resin composition according to the present invention, the content of the acrylic polymer having a ring structure in the main chain is from 51% by weight to 75% by weight, and the vinyl cyanide-based monomer unit and the aromatic A thermoplastic resin composition in which the content of a copolymer containing a vinyl monomer unit is 25% by weight or more and 49% by weight or less, wherein the weight-average molecular weight when heated at 290 ° C. for 10 minutes in a nitrogen atmosphere is measured. The thermoplastic resin composition has an increase rate of 7% or less and the number of bubbles measured by the following method is less than 50 / g.
Number of air bubbles: The thermoplastic resin composition dried in an oven at 90 ° C. for 24 hours is loaded into a cylinder of a melt indexer specified in JIS K7210, held at 260 ° C. for 20 minutes, and extruded into a strand. The number of bubbles existing in the strand extruded between the upper mark line and the lower mark line of the piston of the melt indexer was counted and converted into the number per 1 g of the resin.

  According to the method for producing the thermoplastic resin composition of the present invention, the amount of the basic substance or the acidic substance used in the neutralization step with respect to the catalyst used in the cyclization step is set within the range of the present application, whereby vinyl cyanide is used. The generation of foreign matter derived from a copolymer containing a monomer and an aromatic vinyl monomer unit can be suppressed.

  Further, in the thermoplastic resin composition of the present invention, the rate of increase in weight average molecular weight when heated at 290 ° C. for 10 minutes under a nitrogen atmosphere is 7% or less, and the number of bubbles during heat retention is less than 50 / g. In addition to having high heat resistance and negative birefringence, it is possible to suppress the generation of foreign matter defects in a negative retardation film obtained by stretching.

  Hereinafter, embodiments of the present invention will be described in detail.

[Acrylic polymer having main chain ring structure]
In the present specification, “acrylic polymer” refers to a polymer having a structural unit derived from a (meth) acrylate monomer in the main chain (hereinafter, referred to as “(meth) acrylate unit”). The “acrylic polymer having a ring structure in the main chain” refers to a polymer containing a (meth) acrylate unit and a ring structure in the main chain.

  A ring structure is a dealcoholization-condensation reaction (hereinafter also referred to as a cyclization reaction) between a hydroxyl group or a carboxyl group in the molecular chain of a (meth) acrylate unit and an ester group in the molecular chain. ) Means a structure formed by proceeding. Examples of the ring structure include a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, an N-substituted maleimide structure, and a maleic anhydride structure.

  The sum of the content of the (meth) acrylate unit and the content of the ring structure in the “acrylic polymer having a ring structure in the main chain” is preferably 50% by weight or more, more preferably in the main chain. Is at least 70% by weight, more preferably at least 90% by weight, particularly preferably at least 95% by weight, most preferably at least 99% by weight.

  The content of the ring structure (excluding the lactone ring structure) in the “acrylic polymer having a ring structure in the main chain” is not particularly limited, but is, for example, 5% by weight to 90% by weight, and 10% by weight to 70% by weight. % By weight, more preferably 10% by weight or more and 60% by weight or less, further preferably 10% by weight or more and 50% by weight or less.

  When the “acrylic polymer having a ring structure in the main chain” has a lactone ring structure in the main chain, the content of the lactone ring structure in the polymer is not particularly limited, but is, for example, 5% by weight or more and 90% by weight or less. 20 to 90% by weight, 30 to 90% by weight, 35 to 90% by weight, 40 to 80% by weight, 45 to 75% by weight in the following order. It will be preferable.

  When the content of the ring structure in the `` acrylic polymer having a ring structure in the main chain '' is excessively small, the heat resistance of the resin composition and the resin molded product obtained by molding the composition are reduced, Solvent resistance and surface hardness may be insufficient. On the other hand, when the content is excessively large, the moldability and the handling property of the resin composition may be reduced.

  The (meth) acrylate unit is, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate N-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate, (meth) acrylic acid Dicyclopentanyl, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2,3 (meth) acrylate , 4,5,6-pentahydroxyhexyl, 2,3,4,5-tetrahydroxy (meth) acrylate Pentyl is a structural unit derived from a monomer such as.

  The “acrylic polymer having a ring structure in the main chain” may contain two or more (meth) acrylate units. Further, the “acrylic polymer having a ring structure in the main chain” preferably contains methyl (meth) acrylate as a (meth) acrylate unit. By containing methyl (meth) acrylate, it is possible to improve the thermal stability of the thermoplastic resin composition obtained by the production method according to the present invention and the resin molded product obtained by molding the composition. .

  The “acrylic polymer having a ring structure in the main chain” may also contain a constituent unit other than the (meth) acrylate unit. Examples of the constituent unit include a constituent unit derived from a monomer containing a hydroxyl group, a constituent unit derived from a monomer containing a carboxylic acid group, and the like. In the production method according to the present invention, in order to introduce a ring structure into the main chain by a cyclization reaction, when polymerizing the above-mentioned “acrylic polymer having a ring structure in the main chain”, the following monomers are copolymerized. Is preferred.

  Examples of the monomer containing a hydroxyl group include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, methyl 2- (hydroxyethyl) acrylate, and the like.

  Examples of the monomer having a carboxylic acid group include monomers such as acrylic acid, methacrylic acid, crotonic acid, 2- (hydroxymethyl) acrylic acid, and 2- (hydroxyethyl) acrylic acid. .

  In the “acrylic polymer having a ring structure in the main chain”, two or more of these monomers may be copolymerized. The monomer containing a hydroxyl group and the monomer containing a carboxylic acid group change into a ring structure by a cyclization reaction, but the `` acrylic polymer having a ring structure in the main chain '' includes a hydroxyl group. A constituent unit derived from an unreacted monomer and / or a constituent unit derived from an unreacted monomer containing a carboxylic acid group may be contained.

  Further, the “acrylic polymer having a ring structure in the main chain” may contain other constituent units. Examples of the other structural unit include styrene, vinyl toluene, α-methylstyrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene, acrylonitrile, methacrylonitrile, methallyl alcohol, allyl alcohol, ethylene, propylene, Examples include structural units derived from monomers such as -methyl-1-pentene, vinyl acetate, 2-hydroxymethyl-1-butene, methyl vinyl ketone, N-vinyl pyrrolidone, and N-vinyl carbazole. The “acrylic polymer having a ring structure in the main chain” may contain two or more of the other structural units.

  The type of the “ring structure” is not particularly limited. For example, at least one selected from a lactone ring structure, a glutaric anhydride structure, a glutarimide structure, an N-substituted maleimide structure, and a maleic anhydride structure can be used.

  Since the Tg of the “acrylic polymer having a ring structure in the main chain” and the acrylic resin composition produced by the production method according to the present invention can be further improved, the ring structure has a glutarimide structure and an anhydrous structure. It is preferably at least one selected from a glutaric acid structure and a lactone ring structure.

  The following formula (1) shows a glutarimide structure and a glutaric anhydride structure.

R ¹ and R ² in the above formula (1) are each independently a hydrogen atom or a methyl group, and X ¹ is an oxygen atom or a nitrogen atom. When X ¹ is an oxygen atom, R ³ does not exist. When X ¹ is a nitrogen atom, R ³ is a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, a cyclohexyl group or a phenyl group. .

When X ¹ is a nitrogen atom, the ring structure represented by the formula (1) is a glutarimide structure. The glutarimide structure can be formed, for example, by imidizing a (meth) acrylate polymer using an imidizing agent such as methylamine.

When X ¹ is an oxygen atom, the ring structure represented by the formula (1) is a glutaric anhydride structure. The glutaric anhydride structure can be formed, for example, by subjecting a copolymer of (meth) acrylic acid ester and (meth) acrylic acid to de-alcoholization and condensation in a molecule.

  The following formula (2) shows an N-substituted maleimide structure and a maleic anhydride structure.

R ⁴ and R ⁵ in the above formula (2) are each independently a hydrogen atom or a methyl group, and X ² is an oxygen atom or a nitrogen atom. When X ² is an oxygen atom, R ⁶ does not exist, and when X ² is a nitrogen atom, R ⁶ is a hydrogen atom, a linear alkyl group having 1 to 6 carbon atoms, a cyclopentyl group, a cyclohexyl group or a phenyl group. .

When X ² is a nitrogen atom, the ring structure represented by the formula (2) is N- substituted maleimide structure. The acrylic resin having an N-substituted maleimide structure in the main chain can be formed, for example, by copolymerizing an N-substituted maleimide and a (meth) acrylate.

When X ² is an oxygen atom, the ring structure represented by the formula (2) is a maleic anhydride structure. The acrylic resin having a maleic anhydride structure in the main chain can be formed by, for example, copolymerizing maleic anhydride and a (meth) acrylate.

  In each of the methods for forming a ring structure as exemplified in the description of the formulas (1) and (2), the polymer used for forming each ring structure has a (meth) acrylate unit as a constituent unit. The resin obtained by the method is an acrylic resin.

  The ring structure is more preferably a lactone ring structure because it does not contain a nitrogen atom in the ring structure and thus is less likely to be colored (yellowing) and has excellent optical properties when formed into a resin molded product. That is, the “acrylic polymer having a ring structure in the main chain” is more preferably an acrylic polymer having a lactone ring structure in the main chain.

  The lactone ring structure that the “acrylic polymer having a ring structure in the main chain” may have in the main chain is not particularly limited, and may be, for example, a 4- to 8-membered ring. For excellent stability, it is preferably a 5- or 6-membered ring, more preferably a 6-membered ring.

  The six-membered lactone ring structure is, for example,

In the above formula (3), R ⁷ , R ⁸ and R ⁹ are each independently a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The organic residue in the above formula (3) is, for example, an alkyl group having 1 to 20 carbon atoms such as a methyl group, an ethyl group, and a propyl group; and an alkyl group having 1 to 20 carbon atoms such as an ethenyl group and a propenyl group. An aromatic hydrocarbon group having 1 to 20 carbon atoms such as a phenyl group and a naphthyl group; the alkyl group, the unsaturated aliphatic hydrocarbon group, and the aromatic hydrocarbon group Wherein at least one of the hydrogen atoms is substituted with at least one group selected from a hydroxyl group, a carboxyl group, an ether group and an ester group.

  The “acrylic polymer having a ring structure in the main chain” may have a structural unit other than the (meth) acrylate unit and the (meth) acrylic unit. Such structural units include, for example, styrene, vinyltoluene, α-methylstyrene, acrylonitrile, methylvinylketone, ethylene, propylene, vinyl acetate, methallyl alcohol, allyl alcohol, 2-hydroxymethyl-1-butene, α- 2- (hydroxyalkyl) acrylic acid esters such as hydroxymethylstyrene, α-hydroxyethylstyrene, methyl 2- (hydroxyethyl) acrylate, 2- (hydroxyalkyl) acrylic acid such as 2- (hydroxyethyl) acrylic acid, It is a structural unit derived from a monomer such as The “acrylic polymer having a ring structure in the main chain” may have two or more of these constituent units.

  The weight average molecular weight of the “acrylic polymer having a ring structure in the main chain” is, for example, in the range of 1,000 to 300,000, preferably in the range of 5,000 to 250,000, and more preferably in the range of 10,000 to 200. Is more preferable, and the range of 50,000 to 200,000 is still more preferable.

  The "acrylic polymer having a ring structure in the main chain" is a cyclized condensation reaction of the acrylic polymer by using an acidic substance or a basic substance as a catalyst, and a ring structure is formed in the main chain of the polymer. (Cyclization step).

  The acryl-based polymer can form a lactone ring structure by a cyclocondensation reaction between a hydroxyl group and an ester group in a molecular chain.

(A. Polymerization step)
Hereinafter, the acrylic polymer as a raw material for forming a lactone ring structure will be described. The acrylic polymer is preferably a vinyl monomer polymer represented by the following formula (4).

In the formula (4), R ¹⁰ and R ¹¹ are each independently a hydrogen atom or a group exemplified as the organic residue in the formula (3).

  Specific examples of the monomer represented by the formula (4) include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, and 2- (hydroxy Examples thereof include normal butyl methyl) acrylate and t-butyl 2- (hydroxymethyl) acrylate.

  Among these, methyl 2- (hydroxymethyl) acrylate and ethyl 2- (hydroxymethyl) acrylate are preferable, and since the effect of improving heat resistance by forming a lactone ring is high, methyl 2- (hydroxymethyl) acrylate ( MHMA) is particularly preferred. The acrylic polymer may be a polymer obtained by copolymerizing two or more of these monomers.

  The acrylic polymer may be a copolymer of the monomer represented by the formula (4) and a monomer having an ester group (excluding the monomer represented by the formula (4)). Good.

Examples of the monomer having an ester group include (meth) acrylate. The (meth) acrylate is a monomer other than the monomer represented by the formula (8) and includes, for example, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, acrylic acid Acrylic esters such as t-butyl, cyclohexyl acrylate, and benzyl acrylate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, cyclohexyl methacrylate, methacryl Methacrylates such as benzyl acrylate;
And the like.

  Among them, methyl methacrylate (MMA) is particularly preferable because a resin having excellent heat resistance and transparency can be obtained by the cyclization condensation reaction.

  When the acrylic polymer is a copolymer of the monomer represented by the formula (4) and the monomer having an ester group, a monomer group for obtaining the acrylic polymer In the above, preferred ranges of the content of each monomer are as follows.

  That is, the content of the monomer represented by the above formula (4) is preferably in the range of 5% by weight to 90% by weight, more preferably in the range of 10% by weight to 70% by weight, and more preferably 10% by weight or more. The range is more preferably 60% by weight or less, and more preferably 10% by weight or more and 50% by weight or less.

  When the content is less than 5% by weight, the amount of lactone rings formed when the acrylic polymer is subjected to a cyclocondensation reaction decreases, and the resulting resin has heat resistance, solvent resistance, and surface resistance. The hardness and the like may be insufficient.

  On the other hand, if the content exceeds 90% by weight, a gel is formed when the acrylic polymer is subjected to a cyclocondensation reaction, and the transparency and moldability of the obtained resin may be reduced.

  The acrylic polymer includes the monomers exemplified above and other monomers, for example, various monomers containing a hydroxyl group, unsaturated carboxylic acids, monomers represented by the following formula (5), and the like. And a copolymer of

In the above formula (5), R ¹² is a hydrogen atom or a methyl group, and X is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, a —OAc group, a —CN group, a —CO—R ^{13 is a} group or —CO—R ¹⁴ , wherein Ac is an acetyl group, and R ¹³ and R ¹⁴ are a hydrogen atom or a group exemplified as an organic residue in the formula (3).

  Here, the various monomers containing a hydroxyl group are monomers other than the monomer represented by the formula (4), for example, α-hydroxymethylstyrene, α-hydroxyethylstyrene, 2- ( 2- (hydroxyalkyl) acrylic acid esters such as methyl (hydroxyethyl) acrylate; 2- (hydroxyalkyl) acrylic acid such as 2- (hydroxyethyl) acrylic acid;

  Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, α-substituted methacrylic acid, and the like. Of these, acrylic acid and methacrylic acid are particularly preferred.

  Examples of the monomer represented by the formula (5) include styrene, vinyl toluene, α-methylstyrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, and vinyl acetate. Of these, styrene and α-methylstyrene are particularly preferred for exhibiting the effects of the present invention. These monomers may be used alone or in combination of two or more.

  When the acrylic polymer is a copolymer of the above-described monomer and the other monomer, in the monomer group for obtaining the acrylic polymer, the other monomer The total content of the body is preferably from 0% by weight to 30% by weight, more preferably from 0% by weight to 20% by weight, more preferably from 0% by weight to 15% by weight, and from 0% by weight to 10% by weight. More preferred in order.

  The acrylic polymer can form a glutaric anhydride structure by a cyclocondensation reaction between a carboxyl group and an ester group in the molecular chain. Examples of the acrylic polymer forming the glutaric anhydride structure include a copolymer of (meth) acrylic ester and (meth) acrylic acid.

  As the (meth) acrylate, the above-mentioned methyl methacrylate (MMA) or the like can be used. As the (meth) acrylic acid, for example, acrylic acid or methacrylic acid can be used.

  The acrylic polymer that forms a glutaric anhydride structure has a structural unit derived from the monomer used to form the polymer. The content of each structural unit in the acrylic polymer is determined according to the content of each monomer contained in the monomer group polymerized to obtain the acrylic polymer.

  As a polymerization method for obtaining an acrylic polymer, a conventionally known method, for example, a method described in JP-A-2007-262396 can be used. In the present specification, the step of performing polymerization for obtaining an acrylic polymer is also referred to as a “polymerization step”. As the polymerization method, it is preferable to obtain the acrylic polymer by solution polymerization since a cyclization condensation reaction of the acrylic polymer can be subsequently performed after obtaining the acrylic polymer. Further, in order to carry out the reaction efficiently, it is preferable to carry out the polymerization under a nitrogen atmosphere.

  The polymerization temperature and polymerization time vary depending on the type and ratio of the monomers used, but the polymerization temperature is preferably from 0 ° C to 150 ° C, more preferably from 80 ° C to 140 ° C. Yes, the polymerization time is preferably 0.5 hours or more and 20 hours or less, more preferably 1 hour or more and 10 hours or less.

  When the acrylic polymer is formed by solution polymerization, examples of the polymerization solvent used include aromatic hydrocarbons such as toluene, xylene and ethylbenzene; ketones such as methyl ethyl ketone and methyl isobutyl ketone; chloroform and dimethyl sulfoxide ( DMSO), tetrahydrofuran and the like. Above all, it is preferable to use aromatic hydrocarbons and ketones as the polymerization solvent, and particularly preferable to use toluene and methyl isobutyl ketone.

  During the polymerization of the acrylic polymer, a polymerization initiator may be added as necessary. Although the polymerization initiator is not particularly limited, for example, cumene hydroperoxide, diisopropylbenzene hydroperoxide, di-t-butyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butylperoxyisopropyl carbonate, t-amyl peroxide Organic peroxides such as oxy-2-ethylhexanoate; 2,2′-azobis (isobutyronitrile), 1,1′-azobis (cyclohexanecarbonitrile), 2,2′-azobis (2-methyl Azo compounds such as isobutyronitrile) and 2,2′-azobis (2,4-dimethylvaleronitrile).

  These polymerization initiators may be used alone or in combination of two or more. The amount of the polymerization initiator to be used may be appropriately set according to the combination of the monomers or the polymerization conditions, and is not particularly limited.

  When the acrylic polymer is formed by solution polymerization, the polymerization product contains, in addition to the acrylic polymer, the polymerization solvent used for the polymerization, but the acrylic polymer is not necessarily removed by removing the solvent. Need not be taken out as a solid.

  As described above, the polymerization product can be introduced into the subsequent cyclization step while containing the solvent. Of course, after the acrylic polymer is taken out as a solid, a solvent more suitable for performing the cyclization step than the solvent used during the polymerization may be added again and introduced into the cyclization step.

  Suitable solvents for performing the cyclization step are not particularly limited, and include, for example, aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; ketones such as methyl ethyl ketone and methyl isobutyl ketone; chloroform, DMSO, and tetrahydrofuran. Although it can be used, it is preferably a solvent of the same type as the solvent that can be used in the polymerization step.

  The acrylic polymer is not necessarily prepared by performing a polymerization reaction, but may be a commercially available product.

(B. Cyclization step)
In the cyclization step in the production method according to the present invention, the cyclization condensation reaction of the acrylic polymer is performed by using an acidic substance or a basic substance as a catalyst to form a ring structure in the main chain of the polymer. This is a step of obtaining an acrylic polymer having a ring structure in the main chain. In the present specification, a catalyst used for a cyclization condensation reaction of an acrylic polymer is also referred to as a cyclization catalyst.

  By forming a ring structure in the main chain by the cyclization condensation reaction, a resin having excellent heat resistance can be obtained. In addition, by adding a cyclization catalyst to the acrylic polymer, side reactions between the monomer and the catalyst and branching and crosslinking during polymerization are suppressed, and the acrylic polymer has excellent thermal stability and mechanical strength. Can be provided.

  As the catalyst, an acidic substance or a basic substance can be used. The acidic substance may be an inorganic substance or an organic substance as long as it can function as a catalyst for the cyclization condensation reaction.

  As the inorganic substance, for example, sulfuric acid, hydrochloric acid, and the like can be used. The above-mentioned inorganic substances may be used alone or in combination of two or more.

  Examples of the acidic substance that is an organic substance include an organic phosphorus compound, an esterification catalyst or a transesterification catalyst such as p-toluenesulfonic acid which is generally used as a catalyst for a cyclocondensation reaction, acetic acid, propionic acid, benzoic acid, and acrylic acid. And organic carboxylic acids such as methacrylic acid.

  Among them, it is preferable to use an organic phosphorus compound as the organic substance. By using an organic phosphorus compound as a cyclization catalyst, the cyclization condensation reaction rate can be improved, and the coloring of the resulting lactone ring-containing acrylic polymer can be significantly reduced. Furthermore, by using an organic phosphorus compound as a cyclization catalyst, there is an advantage that a decrease in molecular weight that can occur when a devolatilization step described below is used in combination can be suppressed, and excellent mechanical strength can be imparted. That's why.

  Examples of the organic phosphorus compound that can be used in the present invention include, for example, alkyl (aryl) phosphonous acids such as methylphosphonous acid, ethylphosphonous acid, and phenylphosphonous acid (however, these are tautomeric alkyl (Aryl) phosphinic acid) and monoesters or diesters thereof; dialkyl (aryl) phosphinic acids such as dimethylphosphinic acid, diethylphosphinic acid, diphenylphosphinic acid, phenylmethylphosphinic acid, phenylethylphosphinic acid and the like; These esters; alkyl (aryl) phosphonic acids such as methylphosphonic acid, ethylphosphonic acid, trifluoromethylphosphonic acid, phenylphosphonic acid and monoesters or diesters thereof; methylphosphinous acid, ethyl Alkyl (aryl) phosphinous acids such as phosphinic acid and phenyl phosphinous acid and esters thereof; methyl phosphite, ethyl phosphite, phenyl phosphite, dimethyl phosphite, diethyl phosphite, diphenyl phosphite Phosphite monoester, diester or triester such as trimethyl phosphite, triethyl phosphite, triphenyl phosphite; methyl phosphate, ethyl phosphate, 2-ethylhexyl phosphate, octyl phosphate, isodecyl phosphate , Lauryl phosphate, stearyl phosphate, isostearyl phosphate, phenyl phosphate, dimethyl phosphate, diethyl phosphate, di-2-ethylhexyl phosphate, diisodecyl phosphate, dilauryl phosphate, distearyl phosphate, distearyl phosphate Isostearyl, diphenyl phosphate, trimethyl phosphate, Phosphoric acid monoesters, diesters or triesters such as triethyl phosphate, triisodecyl phosphate, trilauryl phosphate, tristearyl phosphate, triisostearyl phosphate, triphenyl phosphate; methylphosphine, ethylphosphine, phenylphosphine, dimethylphosphine Mono-, di- or tri-alkyl (aryl) phosphines such as, diethyl phosphine, diphenyl phosphine, trimethyl phosphine, triethyl phosphine, triphenyl phosphine; methyl dichlorophosphine, ethyl dichlorophosphine, phenyl dichlorophosphine, dimethylchlorophosphine, diethylchloro Alkyl (aryl) halogen phosphines such as phosphine and diphenylchlorophosphine; methyl phosphine oxide, ethyl phosphine Mono-, di- or tri-alkyl (aryl) phosphines such as fin, phenylphosphine oxide, dimethylphosphine oxide, diethylphosphine oxide, diphenylphosphine oxide, trimethylphosphine oxide, triethylphosphine oxide, triphenylphosphine oxide; tetramethyl chloride Halogenated tetraalkyl (aryl) phosphonium such as phosphonium, tetraethylphosphonium chloride and tetraphenylphosphonium chloride; and the like.

  These organic phosphorus compounds may be used alone or in combination of two or more. Of these organophosphorus compounds, alkyl (aryl) phosphonous acid, phosphite monoester or diester, phosphoric acid monoester or diester, and alkyl (aryl) phosphonic acid have high catalytic activity and low coloring property. Preferably, alkyl (aryl) phosphonous acid, phosphoric acid monoester or diester, phosphoric acid monoester or diester are more preferred, and alkyl (aryl) phosphonous acid, phosphoric acid monoester or diester is particularly preferred.

  As described above, the acidic substance may be an organic substance or an inorganic substance, but from the viewpoint of operability that it can be dissolved or dispersed in an organic solvent and from the viewpoint of suppressing the coloring of the reaction product, It is preferable to use

  As mentioned above, the use of basic substances as cyclization catalysts is also possible. The basic substance is not particularly limited as long as it can function as a catalyst for the cyclization condensation reaction. For example, a metal carboxylate, a metal complex, a metal oxide and the like can be mentioned. A metal carboxylate and a metal oxide are preferable, and a metal carboxylate is particularly preferable.

  The metal is not particularly limited as long as it does not hinder the physical properties of the resin composition and does not cause environmental pollution at the time of disposal. For example, alkali metals such as lithium, sodium and potassium; magnesium and calcium , Strontium, barium and the like; alkaline earth metals; zinc; zirconium;

  The carboxylic acid constituting the metal carboxylate is not particularly limited, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, Lauric, myristic, palmitic, stearic, behenic, tridecanoic, pentadecanoic, heptadecanoic, lactic, malic, citric, oxalic, malonic, succinic, fumaric, maleic, adipic, etc. Is mentioned.

  The organic component in the metal complex is not particularly limited, and examples include acetylacetone. Examples of the metal oxide include zinc oxide, calcium oxide, and magnesium oxide, and zinc oxide is preferable.

  Further, compounds of Group 12 elements described in JP-A-2009-144112 can also be suitably used as the basic substance. Among them, a zinc compound is preferably used because it has a large effect of promoting the cyclization reaction.

  Specific types of the zinc compound are not particularly limited, and examples thereof include organic zinc compounds such as zinc acetate, zinc propionate, and zinc octylate; inorganic zinc compounds such as zinc oxide, zinc chloride, and zinc sulfate; and trifluoromethanesulfonic acid. An organic zinc compound containing fluorine such as zinc can be suitably used.

  The amount of the cyclization catalyst used in performing the cyclization condensation reaction is not particularly limited. For example, the amount is preferably 0.001% by weight or more based on the acrylic polymer having a ring structure in the main chain. % By weight, more preferably 0.01 to 2.5% by weight, still more preferably 0.01 to 1% by weight, particularly preferably 0.05 to 0.5% by weight. is there.

  If the amount of the catalyst is less than 0.001% by weight, the reaction rate of the cyclization condensation reaction may not be sufficiently improved. Conversely, if the amount of the catalyst exceeds 5% by weight, the obtained resin may be colored, or the resin may be cross-linked to make melt molding difficult.

  The timing of adding the catalyst is not particularly limited. For example, the catalyst may be added during the polymerization step, may be added after the polymerization step, or may be added at both of them. The catalyst may be added while heating during or after the polymerization, or heat treatment may be performed at a high temperature after the addition of the cyclization catalyst.

  The method of heating in the cyclization condensation reaction is not particularly limited, and a conventionally known method may be used. For example, a polymerization solution containing a polymerization solvent obtained in the polymerization step may be subjected to heat treatment as it is, or may be subjected to heat treatment after devolatilization of the solvent. It is also a preferred embodiment that the cyclization reaction is performed in a solution state in a pressure-resistant device such as an autoclave at a temperature of 200 ° C. or higher, and the cyclization reaction is accelerated at a high temperature.

  Alternatively, the devolatilization treatment can be performed using a vacuum furnace for removing volatile components, a heating furnace or a reactor equipped with a devolatilizer, an extruder equipped with a devolatilizer, or the like. In the present invention, one of the preferred embodiments is to heat-treat the polymerization solution containing the catalyst under pressure.

  After heating in a state containing the polymerization solvent and the cyclization catalyst, the cyclization is further performed by heating to 200 ° C. or more under pressure in a pressure-resistant device, thereby preventing the cyclization degree without deterioration in a devolatilization step described later. And an acrylic polymer having a ring structure in the main chain which is high in heat resistance and excellent in heat resistance can be obtained in a solution state.

  Reactors that can be employed during the cyclization condensation reaction are not particularly limited, and include, for example, an autoclave, a kettle-type reactor, a devolatilization device including a heat exchanger and a devolatilization tank, and the like. A vented extruder suitable for a cyclization reaction using a devolatilization step at the same time can also be used.

  The heating temperature and the heating time are not particularly limited. For example, when an autoclave is used, the heating temperature is preferably 40 ° C. or more and 300 ° C. or less, and the heating time is preferably 1 hour or more and 20 hours or less. More preferably, it is 2 hours or more and 10 hours or less. Taking such a heating temperature and a heating time is preferable because it is possible to reduce the possibility of causing a problem such as a decrease in the cyclization reaction rate and coloring or decomposition of the resin.

  As described above, by performing the cyclization condensation reaction using the above acidic substance or basic substance as the cyclization catalyst, the cyclization reaction between the hydroxyl group or carboxyl group and the ester group present in the molecular chain of the acrylic polymer is performed. As a result, an acrylic polymer having a lactone ring structure or a glutaric anhydride structure in the main chain can be obtained.

  Further, by copolymerizing the acrylic polymer with the N-substituted maleimide or maleic anhydride, an acrylic polymer having an N-substituted maleimide structure or a maleic anhydride structure in the main chain can be obtained.

  Furthermore, an acrylic polymer having a glutarimide structure can be obtained by adding an imidizing agent to the acrylic polymer. Examples of the imidizing agent include aliphatic amines such as methylamine, ethylamine, n-propylamine, i-propylamine, n-butylamine, i-butylamine, tert-butylamine, n-hexylamine and cyclohexylamine; aniline, toluidine Urea compounds such as urea, 1,3-dimethylurea, 1,3-diethylurea, and 1,3-dipropylurea, which generate amines by heating; and the like.

(C. Devolatilization step)
In the present invention, a devolatilization step described in JP-A-2000-230016, JP-A-2007-262396, JP-A-2007-262399, or the like can be used in combination with the cyclization reaction.

  The devolatilization step refers to a step of removing volatiles such as a solvent and a residual monomer and an alcohol by-produced in the cyclization step, if necessary, under reduced pressure and heating conditions. By this step, it is possible to reduce the possibility of causing problems such as coloring due to deterioration during molding based on residual volatile components in the generated resin and molding defects such as bubbles and silver streaks.

  A preferred embodiment of the devolatilization step includes a method in which the cyclization condensation reaction is performed in the presence of a solvent, and the devolatilization step is used in combination with the cyclization condensation reaction. In this case, a mode in which the devolatilization step is used in combination throughout the cyclization condensation reaction, and a mode in which the devolatilization step is used only in part of the cyclization condensation reaction but not in the entire process. In the method using the devolatilization step in combination, the alcohol by-produced in the condensation cyclization reaction is forcibly devolatilized and removed, so that the equilibrium of the reaction is advantageous to the production side.

  In the method using the devolatilization step in combination, the alcohol by-produced in the condensation cyclization reaction is forcibly devolatilized and removed, so that the equilibrium of the reaction is advantageous to the production side.

  In the case of using the devolatilization step in combination throughout the cyclization condensation reaction, the apparatus to be used is not particularly limited, but in order to more effectively perform the present invention, a devolatilization apparatus including a heat exchanger and a devolatilization tank Or a vented extruder, it is preferable to use one in which the devolatilizing device and the extruder are arranged in series, and it is more preferable to use a devolatilizing device or a vented extruder comprising a heat exchanger and a devolatilizing tank. preferable.

  When using a devolatilizing device comprising the heat exchanger and a devolatilizing tank, the reaction treatment temperature is preferably in the range of 150 ° C to 350 ° C, and more preferably in the range of 200 ° C to 300 ° C. If the reaction treatment temperature is lower than 150 ° C., the cyclization reaction may be insufficient and the remaining volatile components may increase, and if it is higher than 350 ° C., coloring or decomposition may occur.

  In the case of using a devolatilizing device comprising the heat exchanger and a devolatilizing tank, the pressure during the reaction treatment is preferably in the range of 931 hPa to 1.33 hPa (700 mmHg to 1 mmHg), and is preferably 798 hPa to 66.5 hPa ( The range is more preferably from 600 mmHg to 50 mmHg). If the pressure is higher than 931 hPa, there is a problem that volatile components including alcohol are likely to remain. If the pressure is lower than 1.33 hPa, there is a problem that industrial implementation becomes difficult.

  When using the extruder with a vent, the vent may be one or more, but it is preferable to have a plurality of vents. When the extruder with a vent is used, the reaction treatment temperature is preferably in the range of 150 ° C to 350 ° C, more preferably in the range of 200 ° C to 300 ° C. If the temperature is lower than 150 ° C., the cyclization condensation reaction may be insufficient and the remaining volatile components may increase. If the temperature is higher than 350 ° C., coloring or decomposition may occur.

  When the extruder with a vent is used, the pressure during the reaction treatment is preferably in the range of 931 hPa to 1.33 hPa (700 mmHg to 1 mmHg), and in the range of 798 hPa to 13.3 hPa (600 mmHg to 10 mmHg). Is more preferred.

  If the pressure is higher than 931 hPa, there is a problem that volatile components including alcohol are likely to remain. If the pressure is lower than 1.33 hPa, there is a problem that industrial implementation becomes difficult.

  In the case of using a devolatilization step in combination throughout the entire cyclization reaction, severe heat treatment conditions may deteriorate the physical properties of the obtained acrylic polymer having a ring structure in the main chain, and therefore, the above-described one is preferable. It is preferable to use a catalyst for the dealcoholation reaction and use a vented extruder or the like under conditions as mild as possible.

  In the case of using a devolatilization step in combination throughout the cyclization condensation reaction, preferably, the polymer obtained in the polymerization step is introduced into a cyclization condensation reaction system together with a solvent. Then, it may be passed again through the above-mentioned reaction system such as a vented extruder.

  The devolatilization step may be a form in which the devolatilization step is not used over the entire cyclization reaction, but is used only in part of the process. For example, the apparatus that produced the polymer is further heated, and if necessary, a devolatilization step is partially used in combination, and the cyclization condensation reaction is allowed to proceed to some extent in advance, and subsequently, the devolatilization step is simultaneously used. This is a form in which the cyclized condensation reaction is performed to complete the reaction.

  In the above-described embodiment in which the devolatilization step is used in combination throughout the cyclocondensation reaction, for example, when the polymer is heat-treated at a high temperature of about 250 ° C. or higher using a twin-screw extruder, the heat history Depending on the difference, partial decomposition may occur before the cyclization reaction occurs, and the physical properties of the resulting acrylic polymer having a ring structure in the main chain may be deteriorated.

  Therefore, before performing the cyclization reaction using the devolatilization step at the same time, if the cyclization reaction is allowed to proceed to some extent in advance, the reaction conditions in the latter half can be relaxed, and the physical properties of the obtained acrylic polymer having a ring structure can be relaxed. This is preferable because deterioration can be suppressed.

  In a particularly preferred embodiment, the devolatilization step is started at a time after the start of the cyclization condensation reaction, that is, the hydroxyl group and ester group present in the molecular chain of the polymer obtained in the polymerization step are previously cyclized. A mode in which a cyclization reaction rate is increased to some extent by performing a condensation reaction, and subsequently, a cyclization condensation reaction is simultaneously performed using a devolatilization step simultaneously.

  Specifically, for example, a cyclization reaction is allowed to proceed to a certain degree of reaction in the presence of a solvent using a kettle-type reactor in advance, and thereafter, a reactor equipped with a devolatilizer, for example, heat exchange A mode in which the cyclization condensation reaction is completed by a devolatilizing device including a vessel and a devolatilizing tank, an extruder with a vent, or the like is preferably exemplified. Particularly in the case of this form, it is more preferable that a cyclization catalyst is present.

  As described above, a method of previously performing a cyclization condensation reaction on the polymer obtained in the polymerization step to raise the cyclization reaction rate to a certain degree, and subsequently performing a cyclization condensation reaction simultaneously using a devolatilization step is a ring-condensation method. This is a preferred mode for obtaining an acrylic polymer having a structure.

According to this embodiment, the cyclization reaction rate is further increased, the glass transition temperature is higher, and an acrylic polymer having a ring structure excellent in heat resistance can be obtained. In this case, as a measure of the cyclization reaction rate, the rate of weight loss at 150 ° C. or more and 300 ° C. or less in dynamic TG measurement is preferably 2% by weight or less, more preferably 1.5% by weight or less. , More preferably 1% by weight or less. The dynamic TG measurement was measured by the following method.
Measuring device: Thermo Plus EVO2 TG-DTA TG8120 (manufactured by Rigaku Corporation)
Measurement conditions: sample amount 5 to 10 mg
Atmosphere: Nitrogen flow 200ml / min
Method: Stepwise isothermal control method (control at a weight reduction rate of 0.005% / sec or less between 60 ° C and 500 ° C)
The reactor that can be employed in the cyclization condensation reaction performed in advance before the cyclization condensation reaction using the devolatilization step simultaneously is not particularly limited, but preferably, an autoclave, a kettle type reactor, a heat exchanger, and a devolatilization tank And a vented extruder suitable for a cyclization reaction using the devolatilization step simultaneously.

(D. Neutralization step)
When the cyclization condensation reaction is performed using an acidic substance or a basic substance as the cyclization catalyst as described above, the remaining catalyst adversely affects the heat resistance of the obtained acrylic resin composition. Need to be neutralized. Since the reaction is a neutralization reaction, when the catalyst is an acidic substance, it is sufficient to neutralize the catalyst using a basic substance. Conversely, when the catalyst is a basic substance, the catalyst is neutralized using an acidic substance. I just need. In this specification, the basic substance or the acidic substance used in the neutralization step is also referred to as a cyclization catalyst deactivator.

  As the above basic substance and acidic substance used in the neutralization step, those described in (b. Cyclization step) can be used. In the neutralization step, the basic substance or the acidic substance may be used alone or in combination of two or more. The basic substance or the acidic substance may be added in any form such as a solid, a powder, a dispersion, a suspension, and an aqueous solution, and is not particularly limited.

  As described above, the present inventors have conventionally produced a thermoplastic resin composition by the method described in Patent Document 2 using a basic substance that is 1 molar equivalent to the amount of the cyclization catalyst used. Was. However, the film obtained by the method described in Patent Document 2 has a problem that there are many foreign matter defects.

  Then, the present inventor has described in detail the relationship between the usage amount of the cyclization catalyst and the usage amount of the basic material or acidic substance when the cyclization catalyst is neutralized with a basic substance or an acidic substance. The amount of the basic substance or the acidic substance was examined, and the function of neutralizing the catalyst was maintained by setting the amount of the basic substance or the acidic substance to 0.2 mol equivalent or more and 0.9 mol equivalent or less with respect to the use amount of the catalyst. As described above, it has been found that the heat resistance of the obtained resin composition can be maintained, the occurrence of foreign matter defects in the stretched film can be suppressed, and the above problem can be solved.

  The “molar equivalent” refers to the number of moles of the basic substance or the acidic substance with respect to 1.0 mole of the catalyst.

  When the amount of the basic substance or the acidic substance used in the neutralization step is less than 0.2 molar equivalents relative to the amount of the catalyst used, the action of neutralizing the catalyst becomes insufficient, and molding is performed. Occasionally, foaming or thickening due to crosslinking between polymers may occur, and the heat resistance, mechanical strength, and moldability of the resulting resin composition may be reduced.

  Further, if the amount of the basic substance or the acidic substance used in the neutralization step exceeds 0.9 molar equivalents relative to the amount of the catalyst used, the amount of foreign matter defects during film formation increases. This causes problems in appearance and optical characteristics.

  As described above, the present inventor has found that the ratio between the amount of the catalyst used and the amount of the basic substance or the acidic substance used in the neutralization step has a large effect on the increase in the number of foreign matter defects in the stretched film. For the first time, it has been found that the problem can be solved by setting the amount of the basic substance or the acidic substance to be 0.2 to 0.9 molar equivalents relative to the amount of the catalyst to be used. Was found for the first time.

  In Examples described later, the amount of the basic substance or the acidic substance used in the neutralization step was set to 0.3 molar equivalent, 0.5 molar equivalent, or 0.7 molar equivalent based on the amount of the catalyst used. In this case, it can be seen that the amount of foreign matter defects in the film is significantly suppressed.

  The amount of the basic substance or acidic substance used in the neutralization step is 0.2 mol equivalent or more from the viewpoint of heat resistance, mechanical strength, moldability and amount of foreign matter defects of the obtained resin composition. It is preferably 9 molar equivalents or less, more preferably 0.3 molar equivalents or more and 0.8 molar equivalents or less, and even more preferably 0.45 molar equivalents or more and 0.75 molar equivalents or less.

  The timing of mixing the basic substance or the acidic substance used in the neutralization step may be after the catalyst is added and the cyclization reaction is sufficiently performed in the production of the acrylic polymer, and before the filtration step described below is performed. It is not particularly limited.

  For example, the above-mentioned basic substance or acidic substance is added at a predetermined stage during the production of the acrylic polymer, or a cyclization catalyst is added to the acrylic polymer and heat treatment is performed to advance the cyclization reaction, and then the above-mentioned base is added. A method of adding a basic substance or an acidic substance or producing an acrylic polymer, and then simultaneously heating and melting the acrylic polymer, the basic substance or the acidic substance, and other components, and kneading; After producing the polymer, a method of dissolving the acrylic polymer, the basic substance or the acidic substance, and other components in a solvent; heating and melting the acrylic polymer, other components, and the like; A method in which a basic substance or an acidic substance is added and kneaded; an acrylic polymer is heated and melted, and the basic substance or the acidic substance and other components are added thereto. How to kneading; and the like.

(F. Filtration step)
The filtration step is a step of filtering the acrylic polymer having undergone the neutralization step using a polymer filter. By the filtration step, foreign substances present in the acrylic polymer can be removed.

  The configuration of the polymer filter is not particularly limited, but a polymer filter having a large number of leaf disk filters arranged in a housing can be suitably used. The filter medium of the leaf disc type filter may be any of a sintered metal fiber nonwoven fabric type, a sintered metal powder type, a laminated wire mesh type, or a hybrid type combining them. The sintered type is most preferred.

  The filtration accuracy of the polymer filter is not particularly limited, but is usually 15 μm or less, preferably 10 μm or less, more preferably 5 μm or less. When the filtration accuracy is 1 μm or less, the residence time of the acrylic polymer is prolonged, so that the thermal deterioration of the polymer is increased and the productivity may be reduced.

The filtration area of the polymer filter with respect to the resin processing amount per time is not particularly limited, and can be appropriately set according to the processing amount of the resin composition. The filtration area is, for example, not less than 0.001 m ² / (kg / h) and not more than 0.15 m ² / (kg / h).

  The shape of the polymer filter is not particularly limited, and is, for example, an inner flow type having a plurality of resin flow ports and a resin flow path in a center pole; And an external flow type in which a resin flow path is provided on the outer surface of the center pole. In particular, it is preferable to use an external flow type in which the number of locations where the resin stays is small.

  The residence time of the resin composition in the polymer filter is not particularly limited, but is preferably 20 minutes or less, more preferably 10 minutes or less, and even more preferably 5 minutes or less. Further, the filter inlet pressure and the filter outlet pressure at the time of filtration are, for example, 3 MPa or more and 15 MPa or less and 0.3 MPa or more and 10 MPa or less, respectively, and the pressure loss (pressure difference between the inlet pressure and the outlet pressure of the filter) is 1 MPa or more. A range of 15 MPa or less is preferable. If the pressure loss is less than 1 MPa, the flow path of the acrylic polymer passing through the filter tends to be biased, and the quality of the obtained acrylic polymer tends to deteriorate. On the other hand, when the pressure loss exceeds 15 MPa, breakage of the polymer filter tends to occur.

  In the manufacturing method according to the present invention, an increase in pressure loss of the polymer filter can be suppressed, and thus an increase in pressure loss of the polymer filter before and after the filtration step can be 0.06 MPa / hr or less. The increase is more preferably 0.05 MPa / hr or less, even more preferably 0.04 MPa / hr or less.

  The temperature of the acrylic polymer introduced into the polymer filter may be appropriately set according to its melt viscosity, for example, from 250 ° C to 300 ° C, preferably from 255 ° C to 300 ° C, and more preferably from 260 ° C to 300 ° C. Is more preferred.

  The specific step of obtaining an acrylic resin composition with less foreign matter and coloring by filtration using a polymer filter is not particularly limited. For example, (1) a process of forming and filtering an acrylic resin composition in a clean environment, and subsequently molding the acrylic resin composition in a clean environment, (2) an acrylic resin composition having a foreign substance or a colored substance Is subjected to a filtration process in a clean environment, followed by a process of molding the acrylic resin composition in a clean environment, and (3) simultaneously filtering the acrylic resin composition having foreign substances or colored substances in a clean environment. Molding process, and the like. The filtration treatment of the resin composition with a polymer filter may be performed a plurality of times for each step.

  The molding is not particularly limited, and may be formed into an arbitrary shape. For example, pelletization using a pelletizer, film formation by extruding and kneading the obtained mixture after pre-blending the film raw material with a conventionally known mixer such as an omni mixer, and the like are possible.

  The mixer used for extrusion kneading is not particularly limited, and for example, a conventionally known mixer such as an extruder such as a single screw extruder or a twin screw extruder or a pressure kneader can be used.

  When the resin composition is filtered by the polymer filter, it is preferable to stabilize the pressure of the resin composition in the filter by installing a gear pump between the extruder and the polymer filter.

  The glass transition temperature of the acrylic polymer having a ring structure in the main chain is preferably 110 ° C. or higher. The temperature is more preferably 115 ° C. or higher, further preferably 120 ° C. or higher. The upper limit of the glass transition temperature is not particularly limited, but is preferably 200 ° C. or lower from the viewpoint of moldability.

  The weight average molecular weight of the acrylic polymer is preferably from 10,000 to 300,000, more preferably from 30,000 to 300,000, still more preferably from 50,000 to 250,000, particularly preferably from 80,000 to 250,000. 000 or more and 200,000 or less.

[Copolymer containing vinyl cyanide monomer unit and aromatic vinyl monomer unit]
The copolymer containing a vinyl cyanide monomer unit and an aromatic vinyl monomer unit is not particularly limited, except that it has a negative intrinsic birefringence. The aromatic vinyl monomer unit used in the copolymer containing a vinyl cyanide monomer unit and an aromatic vinyl monomer unit is not particularly limited, and includes, for example, styrene, vinyl toluene, α -Methylstyrene, α-hydroxymethylstyrene, α-hydroxyethylstyrene, chlorostyrene and the like. The content of the aromatic vinyl monomer unit of the copolymer containing the vinyl cyanide monomer unit and the aromatic vinyl monomer unit is preferably 10% by mass or more, more preferably 30% by mass or more, Particularly preferably, it is 50% by mass or more. Examples of the vinyl cyanide monomer unit include acrylonitrile, methacrylonitrile, and the like, and acrylonitrile is preferable.

  Specific types of the copolymer containing a vinyl cyanide-based monomer unit and an aromatic vinyl-based monomer unit are not particularly limited. For example, an acrylonitrile-styrene copolymer, an acrylonitrile-styrene-maleimide copolymer And so on.

  Incidentally, whether the copolymer containing a vinyl cyanide monomer unit and an aromatic vinyl monomer unit is compatible with the acrylic polymer having a ring structure in the main chain, whether both are determined It can be confirmed by measuring the Tg of the resin obtained by mixing by the method described below. Generally, if only one Tg of the composition is confirmed, a copolymer containing a vinyl cyanide-based monomer unit and an aromatic vinyl-based monomer unit is an acrylic having a ring structure in the main chain. It can be said that the polymer has compatibility with the polymer.

  When the copolymer containing the vinyl cyanide-based monomer unit and the aromatic vinyl-based monomer unit is an acrylonitrile-styrene copolymer, the aromatic vinyl-based monomer in all the constituent units of the copolymer is used. Although the ratio occupied by the unit is not particularly limited, it is usually sufficient if it is in the range of 60% by weight or more and 80% by weight or less.

  When the copolymer containing a vinyl cyanide-based monomer unit and an aromatic vinyl-based monomer unit is an acrylonitrile-styrene-maleimide copolymer, an aromatic vinyl-based monomer in all constituent units of the copolymer is used. The proportion occupied by the body unit is not particularly limited, but may be usually in the range of 55% by weight to 80% by weight.

  The copolymer containing a vinyl cyanide monomer unit and an aromatic vinyl monomer unit has a copolymer containing a vinyl cyanide monomer unit and an aromatic vinyl monomer unit in the graft chain. It may contain a rubbery polymer. Examples of the rubbery polymer having a copolymer containing a vinyl cyanide-based monomer unit and an aromatic vinyl-based monomer unit in a graft chain include acrylic rubber, butadiene rubber, ethylene-propylene rubber, and acrylonitrile-styrene copolymer. ASA resin, ABS resin, and AES resin grafted with the union are mentioned, because they do not lower the negative intrinsic birefringence of a copolymer containing a vinyl cyanide-based monomer unit and an aromatic vinyl-based monomer unit. ASA resins are particularly preferred.

  The weight average molecular weight of the copolymer containing a vinyl cyanide-based monomer unit and an aromatic vinyl-based monomer unit is preferably from 10,000 to 500,000, more preferably from 50,000 to 300,000. It is.

[Thermoplastic resin composition]
The thermoplastic resin composition obtained by the production method according to the present invention contains the acrylic polymer having a ring structure in the main chain, the vinyl cyanide monomer unit, and the aromatic vinyl monomer unit. And a copolymer. The content of the copolymer containing the vinyl cyanide-based monomer unit and the aromatic vinyl-based monomer unit in the acrylic resin composition is from 25% by weight to 49% by weight, more preferably 30% by weight. % To 45% by weight, more preferably 30% to 41% by weight. Thereby, in addition to the excellent transparency and heat resistance, mechanical strength, moldability, and the like, the acrylic resin composition can obtain a negative retardation film by stretching. Foreign matter defects of the retardation film can be greatly reduced.

  The thermoplastic resin composition contains, as components other than the acrylic polymer having a ring structure in the main chain and the copolymer containing the vinyl cyanide-based monomer unit and the aromatic vinyl-based monomer unit, other components. , A thermoplastic resin, an antioxidant, and other additives.

  Other thermoplastic resins include, for example, olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly (4-methyl-1-pentene); vinyl chloride; halogen-containing polymers such as chlorinated vinyl resin; polystyrene; Styrene polymers such as styrene-methyl methacrylate copolymer; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamides such as nylon 6, nylon 66, nylon 610; polyacetal: polycarbonate; polyphenylene oxide; polyphenylene sulfide: poly Ether ether ketone; polysulfone; polyethersulfone; polyoxypendylene; polyamideimide; polybutadiene rubber.

  As the acid value antioxidant, for example, an antioxidant, for example, a phenol-based antioxidant, a thioether-based antioxidant, a phosphoric acid-based antioxidant, and the like can be used. The antioxidants exemplified in JP-A No. 5-2,878 can be suitably used.

  The content of the antioxidant in the acrylic resin composition is, for example, 0% by weight or more and 1% by weight or less, and 0% by weight or more and 0% by weight or less, based on 100% by weight of the thermoplastic resin composition of the present invention. The content is preferably 5% by weight or less, more preferably 0% by weight or more and 0.3% by weight or less, further preferably 0.001% by weight or more and 0.1% by weight or less.

  As other additives, for example, stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fiber and carbon fiber; near infrared absorbers; tris (dibromopropyl) phosphate, triallyl phosphate; Flame retardants such as antimony oxide; antistatic agents represented by anionic, cationic and nonionic surfactants; coloring agents such as inorganic pigments, organic pigments and dyes; organic fillers, inorganic fillers; Plasticizers; lubricants; flame retardants and the like.

  The content of the other additive in the acrylic resin composition is, for example, 0% by weight or more and 5% by weight or less, and 0% by weight or more and 2% by weight when the acrylic resin composition is 100% by weight. Or less, more preferably 0 to 0.5% by weight.

The rate of increase in the weight average molecular weight of the obtained thermoplastic resin composition due to heating is preferably 7% or less, more preferably 6% or less, and still more preferably 3% or less. If the rate of increase of the weight average molecular weight by heating is more than 7%, the amount of foreign matter defects at the time of film formation increases, and thus problems in appearance and optical characteristics arise. The rate of increase of the weight average molecular weight of the obtained thermoplastic resin composition due to heating is determined based on the method described in Examples. That is, the prepared thermoplastic resin composition (weight 10 mg) was set on a thermobalance, heated under a nitrogen flow atmosphere at a flow rate of 200 mL / min, and heated by the following temperature raising program, and the temperature was maintained. The weight average molecular weight W2 was determined using chromatography (GPC), and the weight average molecular weight increase rate by heating {(W2-W1) / W1} × 100 was determined using the weight average molecular weight W1 before heating.
-Heating program-
Step 1: From room temperature (20 ° C.) to 290 ° C. at a heating rate of 10 ° C./min. Step 2: From the point when the temperature reaches 290 ° C., hold at that temperature for 10 minutes. Step 3: Hold for 10 minutes. Cool to room temperature (20 ° C)-GPC measurement conditions-
System: Tosoh GPC system HLC-8220
Developing solvent: chloroform (Wako Pure Chemical Industries, special grade)
Solvent flow rate: 0.6 mL / min System: Tosoh column: TSK-GEL SuperHZM-M 6.0 × 150 Two in-line guard column: TSK-GEL SuperHZ-L 4.6 × 35 One reference column: TSK-GEL SuperH-RC 6.0 × 150 Two in-line eluent: chloroform Flow rate: 0.6 mL / min Column temperature: 40 ° C.
The number of bubbles generated by heating the obtained thermoplastic resin composition is preferably 50 or less, more preferably 30 or less, still more preferably 20 or less, and particularly preferably 10 or less. When the number of bubbles generated by heating is more than 50, the amount of foaming at the time of film formation becomes large, and thus there are problems in appearance and film forming properties. The number of bubbles generated by heating the obtained thermoplastic resin composition is determined based on the method described in Examples. That is, the thermoplastic resin composition dried in an oven at 90 ° C. for 24 hours is filled into a cylinder of a melt indexer specified in JIS-K7210, held at 260 ° C. for 20 minutes, and extruded into a strand. The number of bubbles of the foam existing between the upper mark line and the lower mark line of the obtained strand was visually counted, and represented by the number per 1 g of the thermoplastic resin composition.

  The metal content of the obtained thermoplastic resin is preferably at most 85 ppm, more preferably at most 80 ppm, further preferably at most 75 ppm, particularly preferably at most 70 ppm.

  The thermoplastic resin composition is not particularly limited, but a copolymer containing an acrylic polymer having a ring structure in the main chain and the vinyl cyanide-based monomer unit and the aromatic vinyl-based monomer unit, and It can be produced by mixing other thermoplastic resins and additives by a conventionally known mixing method. For example, a method of pre-blending with a mixer such as an omni mixer and then extruding and kneading the resulting mixture can be employed. In this case, the kneading machine used for extrusion kneading is not particularly limited, and for example, a single-screw extruder, an extruder such as a twin-screw extruder, a pressure kneader, or the like, for example, a conventionally known kneader may be used. Can be. The molding temperature is preferably from 200 to 350C, more preferably from 250 to 300C, still more preferably from 255 to 300C, particularly preferably from 260 to 300C.

  The application of the negative retardation film obtained by stretching the thermoplastic resin of the present invention is not particularly limited, and can be used for the same applications as conventional retardation films. More specifically, the negative retardation film obtained by stretching the thermoplastic resin of the present invention can be used as an optical compensation film in an IPS mode or an OCB (optically compensated birefringence) mode LCD.

  The method of forming the thermoplastic resin composition into a film is not particularly limited. When the thermoplastic resin composition is in the form of a solution, it may be cast, for example. When the thermoplastic resin is solid and plastic, a molding technique such as melt extrusion or press molding may be used.

  The method for uniaxially or biaxially stretching the obtained resin film is not particularly limited, and may be in accordance with a known method. The uniaxial stretching is typically a free-end uniaxial stretching that allows a change in the width direction of the film. Fixed-end uniaxial stretching in which the change in the width direction of the film is fixed is also possible. The biaxial stretching is typically sequential biaxial stretching, but simultaneous biaxial stretching in which longitudinal and transverse stretching are simultaneously performed can also be suitably used. Furthermore, stretching in the thickness direction or stretching in an oblique direction with respect to the film roll is also possible. The stretching method, the stretching temperature and the stretching ratio may be appropriately selected according to the desired optical properties and mechanical properties. The method for uniaxially or biaxially stretching the obtained resin film is not particularly limited, and may be in accordance with a known method. The uniaxial stretching is typically a free-end uniaxial stretching that allows a change in the width direction of the film. Fixed-end uniaxial stretching in which the change in the width direction of the film is fixed is also possible. The biaxial stretching is typically sequential biaxial stretching, but simultaneous biaxial stretching in which longitudinal and transverse stretching are simultaneously performed can also be suitably used. Furthermore, stretching in the thickness direction or stretching in an oblique direction with respect to the film roll is also possible. The stretching method, the stretching temperature and the stretching ratio may be appropriately selected according to the desired optical properties and mechanical properties.

  The number of foreign matter defects in the negative retardation film obtained by stretching the thermoplastic resin of the present invention is preferably 15 or less, more preferably 10 or less, and still more preferably 5 or less. The number of foreign matter defects of the negative retardation film obtained by stretching the thermoplastic resin of the present invention is determined based on the method described in Examples. That is, defect detection was performed by an automatic defect inspection apparatus, and then, using a laser microscope, foreign particle defects of 20 μm or more were counted among the detected foreign particle defects.

(Increase rate of weight average molecular weight by heating)
The rate of increase of the weight average molecular weight due to heating of the thermoplastic resin composition was determined as follows.

The prepared thermoplastic resin composition was heated using a thermobalance (manufactured by Rigaku, Thermo Plus Evo Tg-8120). Specifically, the thermoplastic resin composition (weight 10 mg) was set on a thermobalance, and heating and temperature holding were performed by the following temperature raising program under a nitrogen flow atmosphere at a flow rate of 200 mL / min.
-Heating program-
Step 1: From room temperature (20 ° C.) to 290 ° C. at a heating rate of 10 ° C./min. Step 2: From the point when the temperature reaches 290 ° C., hold at that temperature for 10 minutes. Step 3: Hold for 10 minutes. Cool to room temperature (20 ° C.) Determine the weight average molecular weight W2 of the thermoplastic resin composition heated by the heating program using gel permeation chromatography (GPC), and determine the weight by heating using the weight average molecular weight W1 before heating. The increase rate of the average molecular weight {(W2−W1) / W1} × 100 was determined.
The measurement conditions were as follows.
System: Tosoh GPC system HLC-8220
Developing solvent: chloroform (Wako Pure Chemical Industries, special grade)
Solvent flow rate: 0.6 mL / min System: Tosoh column: TSK-GEL SuperHZM-M 6.0 × 150 Two in-line guard column: TSK-GEL SuperHZ-L 4.6 × 35 One reference column: TSK-GEL SuperH-RC 6.0 × 150 Two in-line eluent: chloroform Flow rate: 0.6 mL / min Column temperature: 40 ° C.
(Yellowness measurement)
The degree of yellowness (YI) of the thermoplastic resin composition was measured by ASTM E313. That is, a solution obtained by dissolving 3 g of the thermoplastic resin composition in 17 g of chloroform was measured using a color difference meter (ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.).

[Measurement of number of bubbles]
The number of bubbles in the thermoplastic resin composition was determined as follows.
The dried thermoplastic resin composition was dried in a 90 ° C. oven for 24 hours, filled in a melt indexer cylinder specified in JIS-K7210, and kept at 260 ° C. for 20 minutes. The number of air bubbles present between the upper and lower marking lines of the extruded and obtained strand was visually counted and expressed as the number per 1 g of the thermoplastic resin composition.

[Film foreign matter defect measurement]
Using an automatic defect inspection apparatus, foreign-substance defects of a 200 mm × 300 mm (A4 size) sheet sample were detected. Then, using a laser microscope, gel defects of 20 μm or more were counted among the detected foreign particle defects. The foreign matter defect inspection was performed three times, and the average number of the three times was taken as the number of A4 size foreign matter defects.

(Refractive index anisotropy)
At the wavelength of 589 nm, the in-plane retardation value Re, the thickness direction retardation value Rth, and the optical axis of the film were measured using Otsuka Electronics RETS-100.
The thickness direction retardation value Rth is defined as an average refractive index of the film measured by an Abbe refractometer, a film thickness d (nm), a retardation value measured at an inclination of 40 ° (Re (40 °)), a three-dimensional value. After obtaining the values of the refractive indices nx, ny, and nz, they were obtained from the following equations. The refractive index in the flow direction of the film was nx, the refractive index in the width direction of the film was ny, and the refractive index in the thickness direction of the film was nz.
Thickness direction phase difference Rth (nm) = d × {(nx + ny) / 2−nz}
In-plane retardation Re = (nx−ny) × d
The film thickness d of the film was measured using a Digimatic micrometer (manufactured by Mitutoyo).
In addition, the inclination direction is measured by measuring Re (S40 °) with the slow axis as the inclination axis and Re (F40 °) with the fast axis as the inclination axis, and Re (S40 °)> Re (F40 °). In the case where Re (S40 °) <Re (F40 °), the fast axis was used as the tilt axis.

(Metal content)
The metal content was measured as a metal atom content using a 5 wt% solution of the thermoplastic resin composition dissolved in methyl ethyl ketone as a sample and using an ICP emission spectrometer (iCAP6500 manufactured by Duo Thermo).
(Example 1)
In a 1000 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe and a nitrogen introduction pipe, 40 parts by weight of methyl methacrylate, 10 parts by weight of methyl 2- (hydroxymethyl) acrylate, and 50 parts by weight of a polymerization solvent Parts by weight of toluene and 0.025 parts by weight of ADK STAB 2112 (manufactured by ADEKA) as an antioxidant were charged, and the temperature was raised to 105 ° C. while passing nitrogen through. At the start of the reflux caused by the temperature rise, 0.05 parts by weight of t-amyl peroxyisononanoate (Lupelox 570, manufactured by Arkema Yoshitomi) was added as a polymerization initiator, and 0.10 parts by weight of t-amyl was added. While dropping peroxyisononanoate over 2 hours, the solution polymerization was allowed to proceed under reflux at about 105 to 110 ° C., and aging was further performed for 4 hours.

  Next, to the obtained polymerization solution, 0.05 parts by weight of 2-ethylhexyl phosphate (Phoslex A-8, manufactured by Sakai Chemical Industry Co., Ltd.) was added as a catalyst (cyclization catalyst) for the cyclization condensation reaction. The cyclization condensation reaction for forming a lactone ring structure was allowed to proceed at 110 ° C. under reflux for 2 hours. Subsequently, the polymerization liquid was passed through a multitubular heat exchanger heated to 240 ° C. to further advance the cyclocondensation reaction.

  Next, the obtained polymerization solution was subjected to a barrel temperature of 280 ° C., a rotation speed of 120 rpm, a degree of pressure reduction of 133 to 800 hPa (100 to 600 mmHg), one rear vent and four forevents (first, second, A side feeder is provided between the third and fourth vents, and a leaf disk type polymer filter (filtration accuracy: 5 μm, filtration area: 0.5 m2) is provided at the tip. It was introduced into a vent-type screw twin-screw extruder (Φ = 50.0 mm, L / D = 53) arranged at a processing rate of 27 kg / hour in terms of resin amount, and devolatilized. At this time, 0.24 kg / hour of ion exchange water was charged from behind the second vent at a rate of 0.05 kg / hour with a separately prepared mixed solution of antioxidant / cyclization catalyst deactivator. Charged at a rate behind the first and third vents, respectively. The mixed solution of the antioxidant / cyclization catalyst deactivator is composed of one part of two kinds of antioxidants (Ilganox 1010 manufactured by Ciba Specialty Chemicals, Asahi) Adecasterb AO-412S manufactured by Denka Kogyo Co., Ltd.) and 3.4 parts of zinc octylate (manufactured by Nippon Kagaku Sangyo, 18% of Nikka Octix zinc) as a cyclizing catalyst deactivator were dissolved in 30.4 parts of toluene. Solution was used. The amount of the cyclization catalyst deactivator used was 0.3 molar equivalent based on the amount of the cyclization catalyst used. In addition, pellets of a styrene-acrylonitrile copolymer (the ratio of styrene / acrylonitrile was 73% by weight / 27% by weight and the weight average molecular weight was 190,000) were charged from the side feeder at a charging rate of 10.8 kg / hour. From the relation with the processing speed, the ratio of the styrene-acrylonitrile copolymer in the thermoplastic resin composition is 40% by weight. The zinc content in the obtained resin was 25 ppm.

Next, the obtained resin pellet was melt-extruded at a temperature of 270 ° C. using a vented single-screw extruder having a T die to form an unstretched film having a thickness of 140 μm. Both ends of the unstretched film are gripped with clips and supplied to a tenter, heated to a temperature of 140 ° C., stretched 1.5 times in the longitudinal direction, and then stretched 2.9 times in the transverse direction at a temperature of 135 ° C. Was done. The film thickness obtained after stretching was 35 μm. Foreign film defect measurement was performed on the unstretched and stretched films.
(Example 2)
The procedure was performed in the same manner as in Example 1 except that the mixed solution of the antioxidant / cyclization catalyst deactivator was introduced at a rate of 0.08 kg / hour from behind the second vent. The amount of the cyclization catalyst deactivator used was 0.5 molar equivalent based on the amount of the cyclization catalyst used. The zinc content in the obtained resin was 40 ppm. The thickness of the obtained film was 138 μm for the unstretched film and 36 μm for the film after stretching. Foreign film defect measurement was performed on the unstretched and stretched films.
(Example 3)
The procedure was performed in the same manner as in Example 1 except that the mixed solution of the antioxidant and the cyclization catalyst deactivator was introduced from behind the second vent at an introduction rate of 0.11 kg / hour. The amount of the cyclization catalyst deactivator used was 0.7 molar equivalent based on the amount of the cyclization catalyst used. The zinc content in the obtained resin was 60 ppm. The film thickness of the obtained film was 139 μm for the unstretched film and 35 μm for the film after stretching. Foreign matter defects were measured for the unstretched and stretched films. Moreover, the refractive index anisotropy of the stretched film was measured.
(Comparative Example 1)
The procedure was performed in the same manner as in Example 1, except that the mixed solution of the antioxidant / cyclization catalyst deactivator was introduced from the rear of the second vent at an introduction rate of 0.16 kg / hour. The amount of the cyclization catalyst deactivator used was 1.0 molar equivalent based on the amount of the cyclization catalyst used. The zinc content in the obtained resin was 90 ppm. The film thickness of the obtained film was 138 μm for the unstretched film, and 35 μm for the film after stretching. Foreign matter defects were measured for the unstretched and stretched films. Moreover, the refractive index anisotropy of the stretched film was measured.
(Comparative Example 2)
The procedure was performed in the same manner as in Example 1 except that the mixed solution of the antioxidant / cyclization catalyst deactivator was not charged from behind the second vent. The resulting resin pellets were melt-extruded at a temperature of 270 ° C. using a vented single-screw extruder having a T die, but could not be formed into a film with strong foaming.

  The results of Examples 1 to 3 and Comparative Examples 1 and 2 are summarized in Tables 1 and 2 below.

  The negative retardation film obtained by stretching the thermoplastic resin of the present invention can be widely used for an image display device based on a liquid crystal display device, like the conventional retardation film. By using this retardation film, the display characteristics of the image display device can be improved.

Claims (8)

The content of the acrylic polymer having a ring structure in the main chain is 51% by weight or more and 75% by weight or less, and the copolymer contains a vinyl cyanide monomer unit and an aromatic vinyl monomer unit. A method for producing a thermoplastic resin composition having a proportion of 25% by weight or more and 49% by weight or less, wherein a cyclocondensation reaction is carried out by using an acidic substance or a basic substance as a catalyst to have a ring structure in the main chain. A cyclization step of obtaining an acrylic polymer, and a neutralization step of neutralizing the catalyst with an acidic substance when using an acidic substance as the catalyst, or a basic substance when using the basic substance as the catalyst. Wherein the amount of the basic substance or acidic substance used in the neutralization step is 0.45 to 0.75 molar equivalents relative to the amount of the catalyst used in the cyclization step. Plasticization Method for producing a resin composition. The method for producing a thermoplastic resin composition according to claim 1, wherein an acidic substance is used as the catalyst, and a basic substance is used in the neutralization step. The method for producing a thermoplastic resin composition according to claim 1, wherein an organic acid is used as the catalyst, and a metal salt of a basic substance is used in the neutralization step. The method for producing a thermoplastic resin composition according to any one of claims 1 to 3, wherein the ring structure has a lactone ring structure. The copolymer containing the vinyl cyanide-based monomer unit and the aromatic vinyl-based monomer unit is an acrylonitrile-styrene copolymer or an acrylonitrile-styrene-maleimide copolymer. The method for producing a thermoplastic resin composition of the above. The content of the acrylic polymer having a ring structure in the main chain is 51% by weight or more and 75% by weight or less, and the copolymer contains a vinyl cyanide monomer unit and an aromatic vinyl monomer unit. A thermoplastic resin composition having a proportion of not less than 25% by weight and not more than 49% by weight, wherein an increase rate of a weight average molecular weight when heated at 290 ° C. for 10 minutes in a nitrogen atmosphere is 7% or less, and measured by the following method. A thermoplastic resin composition wherein the number of bubbles to be produced is less than 10 / g .
Number of air bubbles: The thermoplastic resin composition dried in an oven at 90 ° C. for 24 hours is loaded into a cylinder of a melt indexer specified in JIS K7210, held at 260 ° C. for 20 minutes, and extruded into a strand. The number of bubbles existing in the strand extruded between the upper mark line and the lower mark line of the piston of the melt indexer was counted and converted into the number per 1 g of the resin. 7. The thermoplastic resin composition according to claim 6, wherein said ring structure has a lactone ring structure. The heat according to claim 6 or 7, wherein the copolymer containing the vinyl cyanide-based monomer unit and the aromatic vinyl-based monomer unit is an acrylonitrile-styrene copolymer or an acrylonitrile-styrene-maleimide copolymer. Plastic resin composition.